Recently, there is extensively used an endoscope whereby organs within a body cavity can be observed by inserting an insertable part of a small diameter into the body cavity and various cures can be made by using a treating tool inserted through a treating tool channel as required.
Among the above mentioned endoscopes, there are a flexible endoscope wherein the insertable part is flexible and can be passed through a bent course from a mouth cavity or the like to observe an object position within a body cavity and a rigid endoscope wherein the insertable part is rigid and is inserted substantially straight.
Further, there are recently suggested various electronic endoscopes wherein each solid state imaging device as a charge coupled device (CCD) is used as an imaging means. Such electronic endoscope has advantages that the resolution is higher than in a fiber scope, it is easy to record and reproduce picture images and such treatments of picture images as the magnification of picture images and the comparison of two pictures are easy.
Now, in the above mentioned rigid endoscope or, for example, a bladder-urethra scope for diagnosing and curing the bladder or urethra, an optical viewing tube (telescope) or, as required, such treating tool as a catheter or forceps is inserted through a sheath as a hollow guide tube inserted into the urethra to make a treatment.
Further, in case the above mentioned rigid endoscope is to be inserted, a hollow sheath is inserted into the urethra and the rigid endoscope is inserted with this sheath as a guide. At this time, an irrigating liquid is required to be fed to the periphery of the affected part through a hollow path between the sheath and endoscope and to be sucked and drained to discharge a body liquid or the like obstructing the observation or diagnosis of the affected part. In the case of incising the swollen prostate with a resectoscope having a handle and optical viewing tube inserted through the sheath, it may be necessary to drain out of the body the incised tissue pieces and blood together with the irrigating liquid. In such case, the irrigating liquid has been fed through an irrigating liquid path formed in the hollow clearance between the inner peripheral surface of an inner sheath having a cylindrical or elliptical cross-section and the outer peripheral surface of the scope having an elliptical outside diameter and inserted through the sheath. This is accomplished by making the sheath in a double structure and has been drained through an irrigating liquid path formed in the hollow clearance between the outer peripheral surface of the sheath and the inner peripheral surface of an outer sheath having a cylindrical cross-sectional shape and having the inner sheath inserted through it.
However, when, as mentioned above, the optical viewing tube and treating tool or the like are inserted through the inner sheath, further the outer sheath is made to cover the inner sheath and the irrigating liquid is fed and drained through such hollow clearance, in case a treating tool of a large diameter is to be inserted, the hollow clearance will become smaller and the amount of the irrigating liquid will also become smaller. Therefore, there have been problems that, in case a treating tool of a large diameter and a large amount of an irrigating liquid are required, the inner and outer sheath diameters must be made large and the pain given to the patient will increase.